STUDY OF A HIGH PERFORMANCE 30 KW HEAT PUMP WITH AN OIL FREE SINGLE SCREW COMPRESSOR

STUDY OF A HIGH PERFORMANCE 30 KW HEAT PUMP WITH AN OIL FREE SINGLE SCREW COMPRESSOR

Project details

Total cost:

Not available

EU contribution:

Not available

Coordinated in:

France

Objective

OMPHALE, FRANCE DEVELOPED AN OIL FREE SCREW COMPRESSOR OF 30 KW WHERE LUBRICATION TAKES PLACE BY THE REFRIGERANT. IN ADDITION TO THE ABSENCE OF OIL (OIL IN THE REFRIGERANT DIMINISH THE COP) THIS SYSTEM HAS TWO OTHER ADVANTAGES.

BY REGULATING THE MASS FLOW OF THE REFRIGERANT IN THE SCREW COMPRESSOR THE HEAT OUTPUT OF THE HEAT PUMP CAN BE REGULATED DOWN TO 50 % WITH A VERY GOOD PART LOAD EFFICIENCY.

THE SECOND ADVANTAGE IS THE USE OF AN "ECONOMIZER". THIS DEVICE CONSISTS OF AN EXPANSION VALVE WHICH EXPANDS THE CONDENSATE, FORMED IN THE CONDENSOR AFTER THE COMPRESSOR, TO A LOWER INTERMEDIATE PRESSURE. THE FLASH GAS IS THEN FED INTO THE COMPRESSOR, THIS INCREASING THE OVERALL EFFICIENCY. NORMALLY SUCH AN ECONOMIZER ONLY WORKS AT FULL LOAD. IN THIS PROJECT A METHOD HAS BEEN DEVELOPED WHERE THE ECONOMIZER IS EFFICIENT ALSO AT PART LOAD OPERATION. THIS METHOD IS BASED ON THE FACT THAT EACH OF THE TWO GEAT WHEELS FORMS MORE OR LESS A COMPRESSOR BY ITSELF. ONE PART IS KEPT AT THE MAXIMUL MASS FLOW AND IS CONNECTED WITH THE ECONOMIZER, IN THE OTHER PART THE MASS FLOW REGULATED.

EFFICIENCIES OF 75 % HAVE BEEN OBTAINED AT FULL LOAD OPERATION. ENDURANCES TESTS OF OVER 2 000 HOURS AND STOP-START TESTS (500 CYCLES) HAVE BEEN CARRIED OUT TO FULL SATISFACTION.